1. Field of the Invention
The invention refers to a suction device for the drainage of wounds. A device of this kind comprises a suction vessel, a connection hose fastened to said suction vessel and adapted to connect the inner space of said suction vessel with a suction conduit. Furthermore, there is provided a clamp for compressing the connection hose, and an indicating device for indicating the pressure difference between the surrounding atmosphere and said inner space. The indicating device comprises an elastically deformable membrane mounted on said suction vessel and provided with a first surface bounding said inner space and a second surface facing away from said inner space. The invention equally refers to the use of the device for the drainage of wounds.
2. Description of the Prior Art
A suction device known from Swiss Pat. No. 605 313 comprises a suction vessel provided on top with an opening adapted to be closed by means of a plug. The plug made of a rubber-like material comprises a connection hose continuous therewith and adapted to be blocked by means of a clamp, the connection hose serving the purpose of connecting a suction conduit to the device, and being arranged to comprise a section thinned out to form a membrane comprising two horns protruding toward the outside. The membrane constitutes--together with the horns--an indicating device adapted to indicate the difference in presence existing between the surrounding atmosphere and the inner space of the suction vessel. As a matter of fact, if a negative or suction pressure exists in the inner space of the suction vessel relative to the surrouding atmosphere, then the membrane, which in relaxed state shows a plane configuration, will curve inwardly, so that the position of the horns connected with the membrane will represent a measure for the value of the suction pressure. The membrane undergoes continuous deformation while it is being stored, from the time of evacuation of the suction vessel to the time the latter is used for wound drainage, with the result, that the membrane will show effects of fatigue and may even undergo plastic deformation. This time duration will frequently amount to several weeks or months. If the suction vessel then is used for wound drainage, then the membrane will fail to return exactly to its original relaxed state. This causes a negative pressure to be indicated and this reading is incorrect because there is no longer any substantial pressure difference. The error in indication of the negative pressure will be larger, the longer the time elapsed between the evacuation of the suction vessel and its use for wound drainage. Indicating devices which are built according to or similar with that of Swiss Pat. No. 605 313 are unsuitable as suction vessels with long time durations between evacuation and use, even if the suction vessel is meant to be used only once. In addition, the accuracy in determining the value of the negative pressure using the suction device of Swiss Pat. No. 605 313 becomes further reduced by virtue of the fact, that the deformation of the membrane caused by the negative pressure is relatively small. This reduced accuracy is because of the comparatively large ratio between the thickness and the surface area of the membrane. A smaller ratio between the thickness and the area of the membrane would have the result, that during the storage time of the evacuated suction vessel the incurring fatigue and plastic deformation of the membrane would be greater. Also, a reduction in the thickness of the membrane would result in increased danger, that gas will pass through the membrane into the inner space of the suction vessel by diffusion. Furthermore, the indicating device of the known suction device possesses no scale of any kind, so that the determination of the pressure with any degree of accuracy is difficult.